Keeping track of your progress through a loop

Thanks to code.org for this video!

Repeating a part of your program is a very common practice in programming. We'll call this looping, and there many different blocks you can use to do it in many different ways.

The block is appropriate if you want to repeat the same behavior for... ever.

The block is great if you want to loop the same behavior a certain number of times.

Sometimes, though, you want to do almost the same thing for a certain number of times, but with a slight variation. For instance:

You want to draw 20 squares on the screen, but each a different size.
You want to draw 100 polygons with different numbers of sides.

Many such situations can be handled by the for block in the Control palette:

for